Photoflash lamp and mount therefor



March 5, 1957 H. J. EPPIG 2,783,632

PHOTOFLASH LAMP AND MOUNT THEREFOR Filed Feb. 28, 1955 IN V EN TOR. HEN? Y .J: EFF/G any I flWZ/VE'.

United States Patent PHOTOFLASH LAMP AND MGUNT THEREFOR Henry I. Eppig, Montclair, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 28, 1955, Serial No. 491,046

2 Claims. ((11. 67--31) This invention relates to photoflash lamps and, more particularly, to an improved mount for foil-filled type photofiash lamps.

' Foil-filled photoflash lamps are normally constructed with a primer material coated on the ends of spaced leads which form a part of the mount, which leads project inwardly within a vitreous, radiation-transmitting envelope and support a lamp firing filament therebetween. The envelope normally encloses an oxidizing atmosphere and a shredded actinic material and is protected from shattering by a radiation-transmitting internal and external coating of lacquer which absorbs the thermal and mechanical shocks generated when the lamps are fired. A typical photoflash lamp construction is illustrated in Fig. 6 of Patent No. 2,383,076 to Pipkin and as therein illustrated the primer-coated portions of the lead ends occupy a substantially vertical orientation, as observed in elevational view, and are substantially parallel, this lead construction Being eoustomary in photo'flash lamp design.

It has been found that when firing such prior art lamps a large portion of the primer material is ejected as a flame from the coated leads in a direction which is generally perpendicular to the axis of each of the coated leads. This results in a directional flash, with the flame moving substantially horizontally in a direction which is substantially perpendicular to the filament of a lamp, i. e., to a line joining the lead ends, since the hot outwardly moving gases ejected from each lead in this direction are augmented by the simultaneous ejection of hot gases from the other lead. This forms a primer blast wave which takes the general direction of a line perpendicular to the plane formed by the leads and through the filament, and the shredded actinie material which is in the path of this blast wave is carried towards the sides of the envelope where the shredded actinic material burns.

There are several objectional features to foil burning on an envelope. The greatest is that the burning foil chars the protective lacquer and cracks the vitreous envelope, thereby causing large char spots to appear on the envelo e. This may result in smoking of the lamp on firing with possible envelope eruption in a few extreme cases. In addition the light output of the lamp is decreased by the foil burning on the envelope since some of the energy of the actinic material is expended in interaction with the lacquer and the glass. Also, where a shredded actinic material is mashed or bunched together when burning, the oxidation is not as elficient as when the actinic material is fairly evenly dispersed on flashing.

It has been suggested to bend SM lamp type lead ends in the same direction in an L shape in order to project the'S M paste primer, upon flashing of the lamp, in the direction of the lamp bulb axis, so that the material has to travel through a greater distance before reaching the bulb wall, thereby more efiiciently oxidizing the actinic material and also decreasing the tendency for cracking of the glass through contact with the hot actinic materials. This has been experimented within foil-type photoflash lamps where a much smaller amount or" actinic ma 2,783,632 Patented Mar...5, 1.95.7

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2 teriat is carried on the leads than in the SM type lamps. It has been found that at the bend of the L the amount of primer which is held is very difficu-lt to control. This results in a great deviation from lamp to lamp in the time required from the moment offl'ashing to the peak of the light output, since any appreciable variation in the. amount of primer contained on the leads will cause a deviation in the time required for the lamp to produce its maximum intensity of flash. Also, where lead ends are bent at right angles in a foil-filled lamp it becomes difficult to insert the. lead-carrying mount into the envelope since the previously load'ed foil: is disturbed and forced toward the top of the envelope by the projecting lead ends.

It is the general object of this invention to avoid and overcome the foregoing and other difiiculties 0t and objections to prior art practices by the provision of an improved mount for a photofiash lamp which will soften the primer blast which is used to ignite the foil- It isanother object of the invention to provide an improved photofl'ash lamp which will have increased light output for an equivalent amount of actinic material.

The aforesaid objects of the invention, and other ob jects which will become apparent as the description proceeds", are achieved by bending the primer-coated portions oi the leads with respect to the uncoated lead portions so that the lead primer-coated portions are bent substantially away from one another through a definite angle.

For a better understanding of the invention reference should behad to the accompanying. drawing wherein: I

Fig. 1 is an elevational view showing a #5 photoflash lamp having the primer-coated inwardly extending. extremities of the leads bent away from one another in accordance with the teachings of this invention;

Fig. 2 is an enlarged elevational view, partly in section; showing the bent primer-coated portions of the leads;

Fig. 3 is an enlarged plan. view, partly in section, of the bent primer-coated lead portions as illustrated in Fig. 2;

Fig. 4 is an enlarged plan view, partly in section, cor responding to Fig. 3, showing an alternative embodiment.

7 Although the principles of this invention are broadly applicable to any type photoflash lamp, the invention may conveniently be employed in conjunction with a #5 type photoflash lamp and hence it has been so'illustrated and will be so described.

With specific reference to the form of the invention illustrated in the drawing, the numeral 10 indicates gen,-

erally a photoflash lamp comprising a radiati on-transm it ting vitreous envelope 12, a mount 14 which includes leads 16 and a filament 18 connected near the inwardly extending extremities of the leads 16. The lamp may be provided with a bayonet-type base 20, of brass for example, cemented to the envelope 12 at its neck and the leads 16 are electrically connected to this base to provide electrical connection for the firing filament 18. In the case of a #5 photoflash lamp the envelope 12 encloses a volume of 2-5 cubic centimeters and the envelope normally contains an oxidizing atmosphere, such as oxygen at a pressure of 600 millimeters, for example. The envelope may be provided with a layer of lacquer on both the inner and outer surfaces to provide against'violent eruptions on firing. The inner lacquer coating may be an acrylic resin, for example, and the outer lacquer coating may be of cellulose acetate, for example. Alter? natively, a single outer coating of cellulose acetate butyrate, for example, may be used to replace the inner and outer coatings. In the case where a single outer lacquer coating is used, the bent lead construction of this inven' tion is particularly useful. in order to prevent burnin '1 from concentrating at points on the envelope wall, which cracks and melts the vitreous envelope and tendstochar the'extern-al lacquer coating; g g y The bent lead construction is shownim enlarged 1/16? in Fig. 2. The primer 22 is coated onto the lead extremity'for a distance of about 3 mm., in the: case of a #5 phototlash lamp and in such a lamp the primer may consist of l milligram of a mixture of 90% zirconium and potassium perchlorate with a small amount of nitrocellulose binder, for example. Primer materials are wellknown and any suitable primer material may be substituted for the specific example as given. v Starting at a point just above that portion of the lead extremity at which the primer coating commences, the lead primer-coated portions 24 are bent with respect to uncoated lead portions so that the lead primer-coated portions are bent substantially away from one another.

The amount of bend given to each lead is fairly critical and the total bend from the vertical should not be less than .and not more than 70 for each lead. Differently expressed, the angle included between the bent portions of the leads should be at least and not more than 140". It the amount of bend in each lead is less than 20, no appreciable advantage will be realized over the straight lead constructions of the prior art. If the amount of bend for each lead exceeds 70", a relatively small angle will be formed between the primer-coated bent lead portions and the rest of the lead, which bend will holdvariable amounts of primer material which in turn will result in an increased average deviation from the designed time interval measured between the point of firing and the point of maximum light intensity, as will be hereinafter explained. The optimum bend for each lead is from 40 to from the vertical, and the optimum included angle between the bent lead sections is thus from 80 to 100.

As explained heretofore, when the primer material 22 ignited by the hot filament 18 on firing the lamp, the primer material is Violently ejected from the lead as a flame to ignite the foil. Due to the fact that the primer as coated takes the form of a thin tube coated over a metallic rod (the lead) a large part of the primer material will be projected as a flame or flash in a direction which is perpendicular to the axis of the coated lead. When the primer-coated portions of the leads are bent as heretofore specified, most of the gases of the flame of the primer material will be ejected in What might be termed cylindrical patterns, which individual cylindrical patterns have the bent lead sections 24 for axes. It is thus desirable to separate, as much as possible, the primer material which is ejected from each lead, in order that the primer blasts from each lead augmentone another as little as possible. It is thus desirable to bend the leads substantially away from one another in order to separate them as much as possible. It is, of course, obvious that when the bent lead portions are fairly close to one another the primer blasts created on firing will supplement one another which resulting blast will bunch more of the foil together and force it against the envelope where it burns.

in fabricating the improved mount of this invention, A

the end sections 24 of the spaced leads 16 are bent substantially away from one another as heretofore described. The filament 18 is then mounted, preferably on the straight section of the leads immediately below the bend so that the length of the filament will be as reproducible as possible, and also so that relatively short filament lengths may be used. The bent sections 24 of the leads 16 and the filament 18 are then dipped into a primer dipping composition consisting, for example, of 10% potassium perchlorate and 90% zirconium primer material with 31 cc. of 2.5% nitrocellulose binder dissolved in amyl acetate per 100 grams of primer material. This viscous primer-dip adheres to both the bent lead sections and to portions of the filament 18 so that thefilarnent makes contact with the coated primer 22. Only a small amount of the primer material adheres to the filament in the form of irregular beads because of the small filament diameter (0.7 mil, e. g.), and substantially all of the coated primer adheres to the leadswhichmay have a diameter of 20 mils, for example.

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As a matter of manufacturing practicality, it is necessary to dip slightly beyond the filament'to insure that the filament 18 is in contact with the coated primer material 22. As the amount of bend in the filament lead is greater, the angle formed between the straight and bent sections of the leads becomes more acute. It has been found that when the bend of the lead end sections 24 exceeds 70", the primer will tend to form a small ball at the point of bend due to its viscosity and surface tension, which accumulation of primer material is not easily controllable. Any appreciable variation in the amount of primer coated onto the leads will introduce a deviation in the time required from ignition of the lamp to the maximum light intensity, which time is normally designed to be 20 milliseconds in a #5 type photofiash lamp, for example.

Tests have been conducted on a large number of #5 type lamps which were fabricated according to the same standards and which test were designed to measure the lnmens-seccnd output as well as the average deviation from the designed time from ignition tomaximum light intensity. Lamps considered in these tests were constructed with straight leads, as in the prior art, with a bend of 45 as per the preferred embodiment of this in vention and with a or L bend. Results of these,-

As will be observed from the above data, the preferred embodiment of this invention has a light output which is approximately 3% better than the straight leads of the prior art. The average deviation for the preferred embodiment is substantially the same as the average deviation for the straight leads of the prior art, but it is noted that the average deviation for the L type leads is relatively poor. Also the lamps incorporating the prior art straight leads showed considerable lacquer charring While in the lamps incorporating the 45 bent leads, lacquer charring was greatly reduced.

it will be recognized that the objects of the invention have been achieved by providing an improved mount construction for a photofiash lamp which softens the primer blast resulting in less charting of the protective lacquer and in increased light output for an equivalent amount of actinic material.

In Fig. 4 is illustrated a possible alternative embodiment wherein the lead primer-coated portions 24a are bent substantially away from one another, but lie in separate planes. The performance characteristics of sucha lead construction are not quite as good as those'of the preferred embodiment of the invention, but such an alter: native structure may have manufacturing advantages in limited cases.

While in accordance with the Patent Statutes one bestknown embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby I claim:

l. A foil-type photofiash lamp comprising a radiation transmitting envelope having a neck andv amount her: metically sealed to said envelope at its'neck, said en velope enclosing an oxidizing atmosphere and a shredded actinic material, said mount having spaced leads extend ing within said envelope andsupporting a filament there} between, a primer material coated on the inwardly ex tendingportionsof said leads, said filament being elec trically connected to said lead primer-coated portions and said lead primer-coated portions being bent withrespect 5 v. to the uncoated lead portions so that said lead primer coated portions are bent substantially away from one another and the angle included therebetween is at least 40 and not more than 140.

2. A foil-type photoflash lamp comprising a radiationtransmitting envelope having a neck and a mount hermetically sealed to said envelope at its neck, said envelope enclosing an oxidizing atmosphere and a shredded actinic material, said mount having spaced leads extending within said envelope and supporting a filament therebetween, a primer material coated on the inwardly extending portions of said leads, said filament being elec- 6 tnically connected to said lead primer-coated portions, and said lead primer-coated portions being bent with respect to the uncoated lead portions so that said lead primer! coated portions are bent substantially away from one an-;

other and the angle included therebetween is at least about 80 and not more than about 100.

Pipkin Aug. 4, 1942 Pipkin Aug. 21, 1945 

